Though dead humans can't come back to life, certain viruses can induce such aggressive, zombie-like behavior.

For instance, rabies—a viral disease that infects the central nervous system—can drive people to be violently mad. 

Combine rabies with the ability of a flu virus to spread quickly through the air, and you might have the makings of a zombie apocalypse.

Unlike movie zombies, which become reanimated almost immediately after infection, the first signs a human has rabies don't typically appear for ten days to a year, as the virus incubates inside the body. 

If the genetic code of the rabies virus experienced enough changes, or mutations, its incubation time could be reduced dramatically, scientists say.

If a rabies virus can mutate fast enough, it could cause infection within an hour or a few hours. That's entirely plausible.

A faster mode of transmission would be through the air, which is how the influenza virus spreads. All rabies has to do is go airborne, and you have the rage virus" like in 28 Days Later.

It's scientifically unheard of for two radically different viruses such as rabies and influenza to borrow traits. 

However, it's theoretically possible—though extremely difficult—to create a hybrid rabies-influenza virus using modern genetic-engineering techniques.

Combine all these things, and you’ll get something like a zombie virus.